The doctoral thesis is based on 8 papers published in peer-reviewed journals and a review of the literature. The papers are published between 1997 and 2013 in cooperation with Sankt Elisabeth Hospital, Herlev Hospital, Glostrup Hospital, Rigshospitalet, Hvidovre Hospital, Amager Hospital, Copenhagen Trial Unit, and Institute of Preventive Medicine, Copenhagen.
Groin injuries in sport are very common and in football they are among the most common and most time-consuming injuries. These injuries are treated very differently around the world. There is no consensus in the literature regarding definitions, examination methods, diagnosis or treatment and in general the level of evidence is very low. There is a need for identification of the painful anatomical structures, how to examine them and how to define clinical entities to develop effective treatment and prevention.

The aim of these studies were:
- To review the literature to create an overview of the ideas and the knowledge in order to plan future studies in this field.
- Develop and test clinical examination techniques of the relevant tendons and muscles in the region.
- Since no evidence-based diagnosis exist; to develop a set of clinical entities to identify the different groups of patients.
- To test the effect of a dedicated exercise program developed for treatment of long-standing adductor-related groin pain in athletes in a randomised clinical trial comparing it to the treatment modalities used at that time.
- To examine the long-term effect of the above mentioned training program for treatment of long-standing adductor-related groin pain.
- To develop a training program for prevention of groin injuries in soccer and test it in a randomised clinical trial.
- To describe the occurrence and presentation in clinical entities of groin injuries in male football and to examine the characteristics of these injuries.
- Evaluate if radiological signs of femuro-acetabular impingement (FAI) or dysplasia affect the clinical outcome of treatment of long-standing adductor-related groin pain, initially and at 8-12 year follow-up.

The main findings of the 8 papers were:

- No randomised trials existed in this area; there was no consensus in the literature and the majority of the literature was Level 4 and 5. From the existing literature and the authors experience an injury mechanism was suggested and the term ‘adductor-related groin injury’ was suggested.
- A well-defined clinical examination of the adductor-, iliopsoas, and abdominal muscles and the symphysis joint for pain, strength, and flexibility was reproducible with only limited intra- and inter-observer variation.
- By utilising a well-defined classification long-standing groin injuries could be classified with a system of clinical entities.
- Adductor-related injuries were most common among soccer players while iliopsoas-related injuries were most common among runners.
- An active exercise program focusing on strength and coordination of the muscles related to the pelvis with specific emphasis on the adductor muscles was very efficient in treating athletes with long-standing adductor-related groin injury. In a RCT it was clearly superior to conventional passive therapy.
- The above-mentioned training program still had a significant effect at 8 – 12 year follow-up compared to the passive program. Especially among soccer players the long-term effect was evident.
- A training program aimed at prevention and based on the ideas of the above-mentioned treatment program could reduce the number of groin injuries in soccer players during a full season with 31%; this was however, not statistically significant.
- In soccer, adductor-related groin injury was the most common injury (51%), followed by iliopsoas-related (30%) and abdominal-related (19%). Injury time was more than four times as long with adductor- and abdominal-related injury in combination. Previous groin injury doubled the risk of groin injury.
- The morphological changes seen on x-ray related to femuro-acetabular impingement and dysplasia in the hip joint did not seem to influence the clinical outcome of the exercise treatment for long-standing adductor-related groin pain. Neither did it cause increased development of osteoarthritis after 10 years.

With these findings an evidence-based suggestion for classification of groin injuries in connection with sport is available. The specific diagnoses that exist within the clinical entities should now be scientifically investigated and differentiated to further develop more specific treatment and prevention strategies. The etiology of the injuries can now be examined scientifically, and measurement methods to examine strength, range of motion and the effect of the treatment based on the patients perception has been developed and can be implemented in the future research.
With the new knowledge about the morphological variations of the hip joint, including FAI and their relation to development of groin pain and early osteoarthritis of the hip joint, a new chapter has been opened offering major scientific challenges. Hopefully this will lead to a better understanding of the injuries related to the pelvis, hip, and groin in connection with physical activity and in time lead to new and even better treatment and prevention strategies.